The work presented is a straightforward comparison of temperature trends, both observed and modelled. The goal is to check the consistency of the two - ie, asking the question "are the observations inconsistent with the models"?

This is approached though a standard null hypothesis significance test, which I've talked about at some length before. The null hypothesis being that the observations are drawn from the distribution defined by the model ensemble. We are considering whether or not this null hypothesis can be rejected (and at what confidence level). If so, this would tend to cast doubts on either or both of the forced response and the internal variability of the models.

It may be worth emphasising right at the outset that our analysis is almost identical in principle to that presented by Gavin on RC some time ago. In that post, he formed the distribution of model results (over two different intervals) and used this to assess how likely a negative trend would be. Here is his main picture:

He argued (correctly) that if the models described the forced and natural behaviour adequately, a negative 8-year trend was not particularly unlikely, but over 20 years it would be very unlikely, though not impossible (1% according to his Gaussian fit).

We have extended that basic calculation in a few ways, firstly by considering a more complete range of intervals (to avoid accusations of cherry-picking on the start date). Also, rather than using an arbitrary threshold of zero trend, we have specifically looked at where the observed trends actually lie (well, we also show where zero lies in the distributions). I don't believe there is anything remotely sneaky or underhand in the basic premise or method. One subtle difference, which I believe to be appropriate, is to use an equal weighting across models rather than across simulations (which is what I believe Gavin did). I don't think there is any reason to give one model more weight just because more simulations were performed with it. In practice this barely affect the results. Another clever trick (not mine, so I can praise it without a hint of boastfulness) is to use not just the exactly matching time intervals from the models to compare to the data, but also to consider other intervals of equal length but different start months. It so happens that the mean trend of the models is very much constant up to 2020 and of course there were no exciting external events like volcanoes, so this gives a somewhat larger sample size with which to characterise the model ensemble. For longer trends, these intervals are largely overlapping, so it's not entirely clear how much better this approach is quantitatively, but it's still a nice idea.

Anyway, without further ado, here are the results. First the surface observations, plotted as their trend overlaying the model distribution:

You should note that our results agree pretty well with Gavin's - over 8 years, the probability of a negative trend is around 15% on this graph, and we don't go to 20y but it's about 1% at 15y and changing very slowly. So I don't think there is any reason to doubt the analysis.

Then the satellite analyses (compared to the appropriate tropospheric temps, so the y axis is a little different):

And finally a summary of all obs plotted as the cumulative probability (ie one-sided p-level):

As you can see, the surface obs are mostly lowish (all in the lower half), and for several of the years the satellite analyses are really very near the edge indeed.

Note that the observational data points are certainly not independent realisations of the climate trend - they all use overlapping intervals which include the most recent 5 years. Really it's just a lot of different ways of looking at the same system. (If each trend length were independent, then the disagreement would be striking, as it's not plausible that all 11 different values would lie so close to the edge, even with the GISS analysis. But no-one is making that argument.)

It is also worth pointing out that this analysis method contradicts the confused and irrelevant calculations that some have previouslypresentedelsewhere in the blogosphere. Contrary to the impression you might get from those links, the surface obs are certainly not outside the symmetric 95% interval (ie below the 2.5% threshold on the above plots), though you can get just past 5% for HadCRU for particular lengths of trend and a couple of the satellite data points do go below 2.5%, particularly those affected by the super-El-Nino of 1998.

As for the interpretation...well this is where it gets debatable, of course. People may not be entitled to their own facts, but they are entitled to reasonable interpretations of these facts. Clearly, over this time interval, the observed trends lie towards the lower end of the modelled range. No-one disputes that. But at no point do they go outside it, and the lowest value for any of the surface obs is only just outside the cumulative 5% level. (Note this would only correspond to a 10% level on a two-sided test). So it would be hard to argue directly for a rejection of the null hypothesis. On the other hand, it is probably not a good idea to be too blase about it. If the models were wrong, this is exactly what we'd expect to see in the years before the evidence became indisputable. Another point to note is that the satellite data shows worse agreement with the models, right down to the 1% level at one point, and I find it hard to accept that this issue has really been fully reconciled.

A shopping list of possible reasons for the results include:

Natural variability - the obs aren't really that unlikely anyway, they are still within the model range

Incorrect forcing - eg some of the models don't include solar effects, but some of them do (according to Gavin on that post - I haven't actually looked this up). I don't think the other major forcings can be wrong enough to matter, though missing mechanisms such as stratospheric water vapour certainly could be a factor, let alone "unknown unknowns"

Models (collectively) over-estimating the forced response

Models (collectively) under-estimating the natural variability

Problems with the obs

I don't think the results are very conclusive regarding these reasons. I do think that the analysis is worth keeping an eye on. Anyone who thinks that even mainstream climate scientists are not wondering about the apparent/possible slowdown in the warming rate is kidding themself. As I quoted recently:

However, the trend in global surface temperatures has been nearly flat since the late 1990s despite continuing increases in the forcing due to the sum of the well-mixed greenhouse gases (CO2, CH4, halocarbons, and N2O), raising questions regarding the understanding of forced climate change, its drivers, the parameters that define natural internal variability (2), and how fully these terms are represented in climate models.

That wasn't some sceptic diatribe, but rather Solomon et al, writing in Science (stratospheric water vapour paper). And there was also the Easterling and Wehner paper (which incidentally also uses a very similar underlying methodology for the model ensemble). Knight et al as well: "Observations indicate that global temperature rise has slowed in the last decade"

So all those who are hoping to burn me at the stake, please put away your matches.

Tuesday, May 25, 2010

Some people on the internets have suggested that ipads are of little practical value. That would be very wrong. In Japanese mountain huts, where the sun rises through the bare windows at 5am, they not just a luxury but a necessity.

Monday, May 24, 2010

Of course this is accompanied by a "greying" of the population and reduction in the workforce as a proportion of the total. One rational response might be to encourage immigration to make up the numbers, but in fact Japan has been kicking out foreigners at quite a rate recently. The reduction in non-Japanese population actually contributed 47,000 to the total decline. This is all part of the current trend towards isolationism. Perhaps they think they can replace workers with robots.

It was OK as long as we didn't walk into the wind. Unfortunately, down there in the white there is a junction at which we had to do just that. The path being invisible, we walked off the edge of the mountain in the snow hoping we would land on a path below. More accurately, James walked - perhaps he could even see where he was going - while I, eyes stinging and being blown around like a little leaf, clung on to him pathetically.

Thursday, May 20, 2010

This is the title of an interesting paper by Zaliapin and Ghil that appeared some time ago on the Arxiv and more recently in peer-reviewed form in NPG. It's presented as a criticism of Roe and Baker, which has already been debunkedenough, so after a quick glance I didn't pay too much attention to it at first. I also know the second author to be extremely clever, so I was worried that it might be really technical. On a second, slower, reading, however, it's actually quite straightforward and very interesting. It also seems rather harsh on R&B, because the criticism applies to a whole host of similar work.

Z&G start with the basic premise that R&B - and indeed all work of this nature - use, that there's a functional relationship between radiation R (at the top of the atmosphere) and the surface temperature T, which we can write as R=R(T,a(T)) where the notation indicates that a(T) is the "feedback" term, that is to say, if we replace a(T) with zero then the function returns the zero-feedback relationship.

We can then perform a Taylor series expansion to investigate how the radiation balance changes with temperature:

DR = dR/dT*DT + dR/da*da/dT*DT + O(DT2)

(read the real paper for more elegant typesetting)

By writing 1/L0 = dR/dT (L0 is the zero-feedback sensitivity) and defining f=-L0*dR/da*da/dT we arrive at the familiar expression

DR = (1-f)/L0 * DT + O(DT2)

Now what everyone does at this point is to drop the last term and use the linear approximation, which can be re-arranged to give

DT = L0/(1-f) * DF

exhibiting the well-known singularity for a feedback of f=1.

What Zaliapin and Ghil point out is really startlingly simple and IMO elegant. They merely observe that if f is close to one, the linear truncation was not justified because the quadratic term is now large enough to matter! Once it is included, the singularity at f=1 goes away, as their Fig 2 shows:

(The feedback factor f cannot be larger than one or the initial equilibrium is unstable, even with the nonlinear term, hence the upper bound on the x-axis is sound.)

I'm not yet sure how much this really matters. We can still get a high sensitivity so long as the nonlinearity is small. AIUI most models do show a fairly, but not perfectly, linear response over quite a range of forcing and temperature, and the existence of complex climate models with sensitivities above 6C implies that such high values are at least not a mathematical impossibility. It may, however, make it harder to justify the sort of pathological "long tail" arguments beloved by some. Of course I've argued against them on a number of grounds already - not least of which is that, from a policy perspective, we are on really shaky ground if all the calls to action have to be based on highly improbable events that we are pretty confident won't happen irrespective of what mitigation we do or do not attempt. In any case, the maths is interesting in its own right.

Maybe the last picktur I'll post from "real Japan", this one is of a restaurant in Takayama that we didn't go to. Instead we had a very memorable meal of prime beef tonkastu*, but I didn't photograph the probably equally good looking restaurant as I was too busy negotiating our entry to the establishment.

*It was a real treat because normal tonkatsu restaurants in our region of Japan don't serve beef, just pork and jumbo shrimp.

Tuesday, May 18, 2010

When Michelin first brought out a guide to Tokyo a few years ago, there was much brouhaha (also here) about how foreign barbarians couldn't possibly be able to properly judge Japan's uniquely unique haute cuisine, and they seemed to hand out stars like confetti, especially to the sort of absurdly pretentious places where you need a personal introduction in order to even be admitted into the restaurant.

I have to wonder what they will find in Kamakura to be worthy of Michelin stars. I mean, I very much enjoy some of the restaurants here - it is far better than you'd find in any normal Japanese town this size, presumably due to the huge numbers of day-trippers and foreign visitors - but there is nothing that I'd really associate with Michelin stars.

Anyway, I'll be interested to see what they say - and maybe they will have one or two new suggestions for us to try.

Monday, May 17, 2010

Hot on the heels of our paper (which is still languishing in the publishing queue, though published on-line) I was rather surprised to come across another paper recently talking about upper bounds on climate sensitivity, and the costs of climate change. It is open access, so you can all read it for yourselves. The authors consider the "long tail" of possible temperature change and how this influences the economic analyses of climate change. They point out that the pathology of Weitzman's result vanishes if an upper bound on climate sensitivity is imposed. They use a Cauchy distribution for sensitivity, and show that the optimal climate policy is fairly insensitive to where this bound is placed, within the range tested of 20-50C. However, they don't appear to justify why these bounds should be used, rather than (say) 500C or 500,000C, at which point the results would probably be rather different.

Though the authors appear to not know about our Climatic Change paper, they actually do cite two of our other papers, in a way that I'm not really enthused by. They interpret us as explicitly ruling out a value for sensitivity greater than 8C, where in fact all of our results are probabilistic and do not arrive at an absolute value (other than any assumed in the prior). But this is only by way of a throwaway comment at the end of their paper, and isn't in any way central to their argument.

Coincidentally, Myles Allen and co are also going on again about how the Jeffreys' Prior solves all the problems of subjectivity (see here for previous). The whole enterprise appears to be a dead end to me and as far as I can tell, they haven't actually demonstrated any practical results, but maybe when he has eliminated all other possibilities he will reluctantly come around to embracing the standard Bayesian interpretation of probability. At least while he is presenting abstruse technical notes on the Arxiv he isn't causing more trouble elsewhere, and it must now be increasingly difficult for him to defend his previous claims. This could make life a little embarassing for the next IPCC report if people don't start producing climate sensitivity estimates that are not based on the now thoroughly discredited uniform prior...

Sunday, May 16, 2010

Oh, I suppose I shouldn't poke fun. Having got their fingers burnt last year - or perhaps I should say, having had their parade thoroughly rained on - the UK Met Office is declining to offer public forecasts, but is still doing "experimental" research on seasonal prediction and has obviously given a nod and a wink to the author of this Times article.

Saturday, May 15, 2010

A new bulletin board for climate science has been set up here. Apparently there used to be a climate section on physicsforums but they closed it down, so one participant (Chris Ho-Stuart) has set one up himself, with the motivation:

Our aim is to support substantive discussion of the science of climate, especially the underlying physics. We focus on ideas that have been published in the mainstream scientific literature. This still allows for all kinds of competing ideas to be considered, while hopefully avoiding distraction from ideas that have no credible basis.

And to save you from the effort of clicking the link, here's the abstract:

McLean et al. (2009) (henceforth MFC09) claim that the El Niño–Southern Oscillation (ENSO), as represented by the Southern Oscillation Index (SOI), accounts for as much as 72% of the global tropospheric temperature anomaly and an even higher 81% of this anomaly in the tropics. They conclude that the SOI is a “dominant and consistent influence on mean global temperatures,” “and perhaps recent trends in global temperatures.” However, their analysis is inappropriate in a number of ways and overstates the influence of ENSO on the climate system. This comment first briefly reviews what is understood about the influence of ENSO on global temperatures and then shows that the analysis of MFC09 greatly overestimates the correlation between temperature anomalies and the SOI by inflating the power in the 2–6 year time window while filtering out variability on longer and shorter time scales. The suggestion in their conclusions that ENSO may be a major contributor to recent trends in global temperature is not supported by their analysis or any physical theory presented in their paper, especially as the analysis method itself eliminates the influence of trends on the purported correlations.

Unlike Eli, our comment was so devastating that the original authors were unable to come up with a coherent reply. Oh, ok, that's not so different from Eli's case then!

Thursday, May 13, 2010

So the Nasty Party is back in power (I told you before, this blog is strictly neutral on political matters) with the help of the weaselly LibDems. I don't really blame the latter, they had little choice given that Lab/Lib was not viable without numerous fringe parties. I don't think there is much chance of it lasting once the economy heads south, but we will wait and see.

The biggest item of interest to me is the possibility of electoral reform, especially as the economy doesn't affect me so much. It has always seemed absurd that the country should have a dominant Govt supported by only about 35-40% of the voters (which means less than 25% of the electorate by the time the turnout has been accounted for). LDs are supposedly set on "proportional representation" but I haven't actually seen them specify this in detail (nor have I looked). Cons have offered a referendum on Alternative Vote. I think this would be a very big improvement on the current system and think that the arguments against are very weak.

First, those in favour of the current system - usually referred to as "first past the post" which seems bizarre when in fact there is no post, and being first to any specific number of votes is not relevant. Wikipedia calls it "Plurality" which is also a bit cryptic. The supporters seem to believe that what this country needs is "Strong Government", which they claim is best achieved by awarding over 50% of MPs to the party with the most votes, even if a large majority of the electorate opposes them. To those who say, look what FPTP has done for the UK over the past few decades, I reply, yes, by all means look at what it has done, and do you really think that it's worth defending? Lurching from a dominant right-wing govt to an dominant ultra-right-wing government every few years just means they spend most of their time trying to undooutdo the damage that their predecessor did. But mostly, I object to its intrinsic unfairness, invitation to tactical voting and the implication that your vote doesn't matter unless you are in a marginal constituency.

Other possible criticisms of PR are that it may remove the local link from voter to MP, and also that it hands too much influence in the hands of fringe parties like the UKIP, BNP and Greens. On the former point, that is true of some approaches, but not AV. As for the latter, obviously Stoat would like this, but not many others. However, all reasonable proposals like STV generally include a threshold that cuts off the loonies, so this seems like generalised scare tactics rather than a sensible argument. And it doesn't apply to AV in the first place.

I'm disappointed that the Electoral Reform Society has chosen to put such a misleading spin on AV, describing AV as "very much like FPTP" and making a set of amazingly weak and duplicated criticisms in its list of "drawbacks". Yes, AV is not fully proportional, but since no-one advocates fully proportional systems in the first place, this seems somewhat of a straw man. And although there is a theoretical opportunity for tactical voting (as there is in all systems) this is hardly plausible in reality. As obvious and substantial benefits over FPTP, there are no "wasted votes" for minor parties, there is a strong incentive to vote honestly rather than tactically, and the outcome would in practice be substantially closer to proportional (as this BBC page shows for the last election). Their preferred option of STV is not perfect either, but they don't have any list of arguments against it at all!

It should not be overlooked that one large advantage of AV is that it would be simple to implement as a change to the current system. It does not require redrawing boundaries, zoning into regional groups, and (perhaps more importantly) nationally-controlled party lists of top-up MPs that some systems involve. The latter would be an easy target for the press and other critics to oppose.

Oh, but that description relates to "In the United Kingdom, particularly in England". Here in Japan, it's merely the dinner-party conversation of the educated internationalised elite at a highly multicultural gathering.

Ever since discovering the cool Yellowstone Ravens last year, I've been trying to enpixelate one of our jungle crows.These birds are big, aggressive, audacious scavengers that shape the way rubbish collection is organised in Japan; it is only put out on the morning of the collection, and covered with netting, or put in crow-proof crates.

It understandable that their relationship with humans is not that great, and I think this might be why they are hard to photograph. They fly away as soon as they see that you are interested in them.

Anyway, this is the best pic so far. I would have liked to have included the tail and more of the red bridge in the photo, but I wasn't quick enough... it flew away before I could frame a better shot.

Monday, May 10, 2010

Sometimes the extra height of the bipod can really make the picktur. I'm so lucky to have a bipod while all the Japanese have to carry stepladders around...

I wonder what would happen if I bought a blue camera with a flip-out screen as an accessory for my bipod so the automatic composition system could work while the "arms" are fully extended. Could it be that the world is even more exciting viewed from 7.5 feet in the air?

Friday, May 07, 2010

Even if only half of the stories (eg) are half true, the widespread failures of the electoral system in the UK are a complete disgrace. It sounds more like some tinpot dictatorship in Africa than a modern "developed" nation.

(FWIW, I gave up trying to maintain my registration on the electoral roll some time ago, it hardly seems fair to vote as a non-taxpaying expat. Besides, the postal system is so broken that I'd been unable to vote the last few times even when registered and even when living in the UK, due to travelling abroad at the wrong time.)

Wednesday, May 05, 2010

We've been having the annual "Golden Week" holidays (just a set of public holidays that all occur sequentially) here in Japan, so on Monday we went on our traditional hilltop walk on the Ten'en Hiking Course around the north end of Kamakura to the famous Zen temple of Kenchoji.

Actually, this pic is an old one - on Monday it was crowded and we walked though fairly briskly. Outside of main holidays and fairly early in the morning it's usually more like this though. Chojuji was open, unusually, so we went in there too.

The centre of town was absolutely heaving so we quickly retired to our peaceful neighbourhood, and the bicycle maintenance job that has been hanging over me for a couple of months...replacing the rear bottom bracket on our tandem, which had developed an alarming degree of wobble.

Regular cyclists will probably know that the bottom bracket tends to be a particularly recalcitrant opponent and is prone to seizing in place. Sitting there at the low point of the frame where all the water and muck collects, it also has a large diameter thread and thus requires a high torque at the best of times. The rear of a tandem in particular has a large load applied with both riders' forces passing through it. With our tandem being aluminium, the threads in the shell are rather weak and prone to damage - plus effectively irrepairable, making it a potentially expensive job to attempt.

I read Zen and the Art of Motorcycle Maintenance fairly recently. Although nominally about motorcycles, it is also a pretty good bike maintenance manual (helped by the authors' habit of using the term "cycle"). The book's term "gumption trap" applies very well to the problem of a knackered bottom bracket - at least in my case. The cod philosophy is a bit annoying, though.

A few hefty blows with my trusty mallet had got one of the cups loose the day before, but didn't make much of an impression on the other side. I was left scratching my head - and thinking up strategies for finding and importing a new frame - when in a moment of inspiration I remembered the 6ft roof bar we had for mounting the tandem on a car roof (brought with us to Japan, but never used here).

Rather to my surprise, it worked, the threads on the shell are still at least somewhat intact (though a fair amount of powdered metal came out) and the new component is now installed. As the old saying almost says - if at first you don't succeed - get a bigger spanner!

Chojuji, in Kamakura, is very exclusive, in that it is always shut. But on Monday it was open and for only 300¥ we got to tour the pristine buildings and garden. The front garden was very like part of Daitokuji in Kyoto - similar moss garden and even similar decoration on the stone paths. Weirdly, SLR photography was forbidden, but anything else was OK, so everyone except me was taking pictures.

Tuesday, May 04, 2010

I'm not going to the EGU meeting this year for a number of reasons, but it seems that increasingly parts of it is coming to me - a development I'm strongly in favour of, of course. There is an official blog here, and a certain amount of live streaming of lectures and all press conferences can be found via links from here (not so much the ordinary science sessions though). It is still on a rather limited basis compared to what you see by actually attending, but hopefully will expand in the future.

The title of one of the "Great Debates" caught my eye: "To what extent do humans impact the Earth's climate?" It has just ended - I listened to the second half - and it seems that you can already get it on demand here.

It appears that reports of the Hachimangu Ginkgo tree's death were greatly exaggerated. After it blew down a couple of months ago, it was mostly chopped up and taken away, but a chunk of root mass was left in place and a section of the main trunk was erected nearby (along with a book of condolences for people to sign), and people have been praying in front of it - and photographing it - ever since.

To the right is the site where the tree originally grew, where there is now a small mound with green shoots of recovery. More surprisingly, the section of trunk which was set up at the left is greening up too! Fresh leaves can clearly be seen on several twigs. I don't think that bit had any roots attached - it looked like it was cut straight across at both ends. I don't know what chance there is of it re-rooting - obviously some trees can grow from cuttings but this seems an extreme case.